Making a category inactive is a useful way of hiding a category that you may not be using temporarily.
To make one or more categories inactive, head to Products in your menu sidebar.
Then click Categories in the main tab across the top of the page.
This is the category index view, displaying all the categories on your site.
To make a category inactive click the check boxes next to the category you wish to make inactive.
Once you have selected the category or categories you wish to make inactive, click the red "Edit X Categories" button to see the bulk editing tools available. In the drop down, click Make Inactive.
Once you have clicked Make Inactive, you will see the status of the categories change from Active to Inactive.